Classifications

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  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/11—Surgical instruments, devices or methods, e.g. tourniquets for performing anastomosis; Buttons for anastomosis
• • A—HUMAN NECESSITIES
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  • A61B17/04—Surgical instruments, devices or methods, e.g. tourniquets for suturing wounds; Holders or packages for needles or suture materials
  • A61B17/0401—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors
• • A—HUMAN NECESSITIES
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• • A—HUMAN NECESSITIES
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  • A61B17/064—Surgical staples, i.e. penetrating the tissue
  • A61B17/0642—Surgical staples, i.e. penetrating the tissue for bones, e.g. for osteosynthesis or connecting tendon to bone
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  • A61B17/08—Wound clamps or clips, i.e. not or only partly penetrating the tissue ; Devices for bringing together the edges of a wound
  • A61B17/083—Clips, e.g. resilient
• • A—HUMAN NECESSITIES
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  • A61B17/1114—Surgical instruments, devices or methods, e.g. tourniquets for performing anastomosis; Buttons for anastomosis of the digestive tract, e.g. bowels or oesophagus
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  • A61B17/122—Clamps or clips, e.g. for the umbilical cord
• • A—HUMAN NECESSITIES
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  • A61C8/00—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools
  • A61C8/0018—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools characterised by the shape
  • A61C8/0033—Expandable implants; Implants with extendable elements
• • A—HUMAN NECESSITIES
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
  • A61F2/2409—Support rings therefor, e.g. for connecting valves to tissue
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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  • A61B17/0401—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors
  • A61B2017/0412—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors having anchoring barbs or pins extending outwardly from suture anchor body
• • A—HUMAN NECESSITIES
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  • A61B17/0401—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors
  • A61B2017/0427—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors having anchoring barbs or pins extending outwardly from the anchor body
  • A61B2017/0437—Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors having anchoring barbs or pins extending outwardly from the anchor body the barbs being resilient or spring-like
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  • A61B2017/0647—Surgical staples, i.e. penetrating the tissue having one single leg, e.g. tacks
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  • A61B2017/1107—Surgical instruments, devices or methods, e.g. tourniquets for performing anastomosis; Buttons for anastomosis for blood vessels
• • A—HUMAN NECESSITIES
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  • A61B2017/1139—Side-to-side connections, e.g. shunt or X-connections
• • A—HUMAN NECESSITIES
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• • A—HUMAN NECESSITIES
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  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/01—Filters implantable into blood vessels
  • A61F2/0105—Open ended, i.e. legs gathered only at one side
• • A—HUMAN NECESSITIES
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/01—Filters implantable into blood vessels
  • A61F2/0108—Both ends closed, i.e. legs gathered at both ends
• • A—HUMAN NECESSITIES
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/01—Filters implantable into blood vessels
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• • A—HUMAN NECESSITIES
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/01—Filters implantable into blood vessels
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• • A—HUMAN NECESSITIES
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  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
  • A61F2002/30003—Material related properties of the prosthesis or of a coating on the prosthesis
  • A61F2002/3006—Properties of materials and coating materials
  • A61F2002/30092—Properties of materials and coating materials using shape memory or superelastic materials, e.g. nitinol
• • A—HUMAN NECESSITIES
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  • A61F2210/00—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
  • A61F2210/0014—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof using shape memory or superelastic materials, e.g. nitinol
  • A61F2210/0023—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof using shape memory or superelastic materials, e.g. nitinol operated at different temperatures whilst inside or touching the human body, heated or cooled by external energy source or cold supply
• • A—HUMAN NECESSITIES
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  • A61F2230/00—Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
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  • A61F2230/0065—Three-dimensional shapes toroidal, e.g. ring-shaped, doughnut-shaped
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  • A61F2230/0093—Umbrella-shaped, e.g. mushroom-shaped

Definitions

• the present invention relates to devices and, more specifically, to medical devices formed from shape memory alloys and a method for use thereof.
• Austenite - high temperature, high symmetry phase includes structures such as the B2 and R structures.
• Martensite - low temperature, low symmetry phase This phase has a different microstructure from that of the austenite phase, but a specimen, i.e device, in this state has substantially the same external shape as it does in the austenite state.
• This state may also be referred to herein as undeformed or cooling-induced martensite, the terms being used interchangeably without any attempt at distinguishing between them.
• Deformed martensite - A martensitic state having a microstructure different from that of undeformed martensite. Devices formed from alloys in this state have an external shape different from their external shape when the alloy is in its undeformed martensitic state.
• Martensitic transformation - dif ⁇ usionless phase transformation of austenite to martensite The reverse martensitic transformation as used herein is the phase transformation wherein martensite is transformed into austenite.
• M d maximum temperature at which it is possible to obtain stress-induced martensite (SIM) or to maintain stress-retained martensite.(SRM)
• SMA -shape memory alloy- An alloy that inter alia has SME, SE, and SEP properties allowing it to recover its original shape after large deformations.
• SMAs are nickel-titanium alloys.
• SEP- superelastic plasticity effect A property of SMA where the alloy recovers its original shape upon unloading, typically, but not necessarily, at isothermal conditions. This effect can occur only if the alloy is deformed at temperatures below A f and unloaded at temperatures above A f .
• SRM- stress-retained martensite - a deformed metastable martensitic state obtained by deformation of martensite at temperatures below A f and by retaining the deformed state by applying a restraining means at temperatures above Af.
• SIM - stress-induced martensite - a deformed martensitic state obtained by deformation of austenite at temperatures above M s .
• phase and "state” will be used interchangeably with no intention at distinguishing between them.
• Shape memory alloys may exhibit both a shape memory effect (SME) and a superelasticity effect (SE).
• SME occurs when a device formed from an SMA is deformed at a reduced temperature with the device returning to its original shape upon heating.
• SE occurs when a device, formed from an SMA, is deformed under a load; the device recovers its original shape upon removal of the load without a change in temperature.
• the recovery mechanisms of SME and SE are both associated with a reversible martensitic transformation. In the case of SME, recovery occurs after heating, while in the case of SE, recovery occurs after removing a load.
• a device made from a shape memory alloy is relatively easily deformed from its original shape to a new shape when cooled below the temperature at which the alloy is transformed from its austenitic to its martensitic state.
• SMA shape memory alloy
• Fig. 1 The curves in Fig. 1 represent the reversible martensitic transformation which determines the shape memory effect (SME) discussed above.
• SME shape memory effect
• Ma represents the temperature at or above which no martensite can exist, regardless of the application of a distorting force.
• the alloy may contain either 100 % austenite or 100% martensite or a mixture of austenite and martensite.
• state (states) that exists (exist) in this temperature range will depend on whether the temperature change is effected from above A f or below M f respectively, as well as the magnitude of the temperature change. This is a result of hysteresis in the martensitic transformation.
• Region 10 represents the stable martensitic phase and region 12 represents the metastable martensitic phase.
• the Clausius-Clapeyron (CC) relationship 14 separates the stable austenitic phase region 16 from the metastable martensitic phase region
• the CC relationship 14 represents the critical stress required to induce martensite as a function of temperature.
• Fig. 3A schematically illustrates the shape memory effect (SME) in a stress versus temperature diagram.
• SME shape memory effect
• a device formed from a SMA is initially cooled 20 from above temperature A f , where the alloy is fully austenitic, to below M s where the alloy starts its transition to the martensitic state.
• the cooled device is then plastically deformed 22 by a stress.
• the deforming force is removed 24 the device retains its deformed shape as indicated by the parallelogram-like shape in the Figure.
• Heating 26 the device to above temperature A f results in a phase transition to 100% austenite and the device reverts substantially to its original shape.
• Fig. 3B is an alternative method of using the shape memory effect (SME).
• SME shape memory effect
• the device shown is formed from an SMA at a temperature above M s and below A f , where the alloy is in its fully austenitic state.
• the austenite is stressed 27 to form deformed martensite (stress- induced martensite).
• the device remains in its deformed state after removing 28 the load.
• heated 29 above A f a phase transition occurs and the alloy transforms to 100% austenite with the device reverting substantially to its original shape.
• the large rectangles and parallelograms represent the undeformed and deformed shapes of macroscopic devices, respectively, as shown schematically in Fig. 4.
• the small circles within these geometrical shapes schematically indicate alloy particles.
• the small squares and parallelograms found within the larger rectangles and parallelograms schematically indicate the microstructure (crystal lattice) of the alloy. From Fig. 4, the changes in microstructure (crystal lattice) that occur when moving from austenite to martensite to deformed martensite are readily apparent.
• SME shape memory effect
• SE superelastic
• Fig. 5 there is illustrated SE behavior when the device is initially in a stable austenitic state, that is at temperatures above A f but below Md. It should be noted that throughout this text all operations take place at temperatures below Ma-
• the device is deformed 34 so as to cause formation of a metastable martensitic state. This state is represented in Fig. 5 by the region above diagonal line 14 representing the CC relationship.
• the martensite formed is commonly referred to as stress-induced martensite (SIM). Removal 36 of the distorting force returns the alloy to its austenitic state and the device elastically reverts to substantially its original shape.
• SIM stress-induced martensite
• the large parallelograms indicate a deformed device in a metastable martensitic state
• the rectangles indicate an undeformed device in its austenitic state.
• the changes in microstructure, i.e. the phase transformation from austenite to deformed martensite in the alloy itself are shown as changes in the small geometrical shapes within the larger parallelograms and rectangles.
• processes 34 and 36 are not shown as overlapping. They may, and often do, occur at the same temperature. In all cases the temperature must be above the SMA's A f temperature and the stress must be above CC. Heating 35 may therefore occur as shown in Fig. 5 provided that the temperature remains below M d
• Carotid angioplasty and stenting are alternatives to surgery for the treatment of atherosclerotic, carotid-artery, and randomized clinical trials.
• the biocompatibility and shape recoverability of self-expanding SMA stents make them useful for this procedure.
• superelastic behavior is used to insert self-expanding stents.
• Self-expanding stents are manufactured with a diameter larger than that of the target vessel, crimped to transform austenite to stress-induced martensite, and restrained in a delivery system (catheter), before being elastically released into the target vessel.
• Recently mesh stents have replaced coil stents.
• Mesh stents provide some advantages compared with coil stents, but the installation into the restraining catheter is problematic. Using SIM elements requires a technical refinement for their installation, since it requires using special restraining instruments. Mesh stents are discussed in, for example, "An Overview of Stent Design" by T. W. Dueling and D. E. Tolomeo published in Proceedings of the International Conference on Shape Memory and Supereleastic Technologies SMST-2000, Ed. S.M. Russell and A.R. Pelton, pp 585-604.
• Bone Fixation discloses a shape-memory alloy bone staple and associated apparatus for deforming the staple by increasing the span length for insertion thereof into the bone.
• the deformation range of the staple allows the staple to revert to its shape when the temperature change provides transformation to the austenitic phase.
• the anastomosis ring includes a length of a wire formed of a shape memory alloy defining a closed generally circular shape, having a central opening, and having overlapping end portions.
• the anastomosis ring and the shape memory alloy assume a plastic or malleable state at a lower temperature, and an elastic state at a higher temperature.
• the anastomosis ring thereby retains a preselected configuration at the lower temperature, and an elastic crimping configuration upon reverting to the second, higher temperature.
• the apparatus includes an anastomosis ring and further includes a length of a wire formed of a shape memory alloy defining a closed generally circular shape, having overlapping end portions.
• the anastomosis ring assumes a plastic or malleable state when at a lower temperature, and an elastic state when at a higher temperature, thereby enabling the anastomosis ring to retain a preselected configuration at the lower temperature, and an elastic crimping configuration upon reverting to the higher temperature.
• the applicator device allows for the introduction and application of the surgical clip into adjacent hollow organ portions, such that the surgical clip compresses together the adjacent walls of the hollow organ portions, and thereafter causes the cutting apparatus to perforate the adjacent pressed together organ walls to provide patency through the joined portions of the hollow organ.
• the clip is formed of a shape memory alloy, which assumes a plastic or malleable state when at a lower temperature, and an elastic state when reaching a higher temperature. The clip retains a preselected configuration at the lower temperature, and an elastic configuration upon reverting to the higher temperature.
• SMAs for medical devices
• US Pat. No. 3,620,212 to Fannon et al. which discloses an SMA intrauterine contraceptive device
• U.S. Pat. No. 3,786,806 to Johnson et al. which discloses an SMA bone plate
• US Pat. No. 3,890,977 to Wilson which discloses an SMA element to bend a catheter or cannula.
• US Pat. No. 4,233,690 to Akins dated November 18, 1980 entitled “Prosthetic Device Couplings,” discloses a prosthetic element securely joined to a natural element of the human body using a ductile metal alloy coupling member.
• the member has a transition-temperature range and can be deformed from its original shape at a temperature below its transition- temperature. Heating the coupling member to a temperature above the transition temperature causes the coupling to try to return to its original shape and effect a secure join.
• SMA-based devices which employ the SME require heating, as well as heating the applicators used in positioning the devices. Typically, heating is needed to bring the alloy to a temperature above its A f temperature (see Figs 3a and 3B). This heating is cumbersome and at times difficult to achieve, particularly if the device is to be positioned inside the body. Heating may damage sensitive biological tissue.
• An additional disadvantage of an SMA device based on the SME is that such a device typically does not provide a "recovered" force over extended periods of time, i.e. long-term compression.
• SMA devices using the SE effect require relatively substantial loads to generate the desired effect as will be discussed herein below.
• the applicator of a device based on the SE effect and positioning of the device is generally complicated often rendering surgery difficult if not impossible.
• the present invention is intended to provide a method for using shape memory alloys (SMA) to provide long-term compression, generally on body tissues.
• SMA shape memory alloys
• the method allows for the use of low loads and the loads are applied at temperatures at which the SMA is at least partially in its martensitic phase.
• the present invention is intended to provide a method for using SMAs which allows for greater shape restoration then prior art methods.
• the present invention is also intended to provide a method for using SMAs having A f temperatures below body temperature.
• the present invention is further intended to provide a method for using SMAs in medical devices where restraining of the device is effected by body tissue.
• the present invention is also intended to provide a method for using SMAs which allows for greater recovery of the applied distorting force.
• the present invention is also intended to provide a method for using devices containing SMAs which allows for easier positioning when using a device applicator.
• the present invention is also intended to provide medical devices formed from SMAs, employing stress-retained martensite and employing the superelastic plasticity (SEP) effect.
• SMAs superelastic plasticity
• a method for utilizing a deformable article of manufacture adapted to have selectable first and second predetermined configurations and being formed at least partly of a shape memory alloy.
• the method includes the steps of: deforming the article under a deforming force from the first predetermined configuration to the second predetermined configuration while the shape memory alloy is, at least partially, in its stable martensitic state and at a first temperature; applying a resisting force to the deformed article of manufacture using a restraining means; heating the article from the first temperature to a second temperature in the presence of the resisting force, thereby transforming the alloy from its stable martensitic state to its metastable stress-retained martensitic state, while the article remains in its second configuration; and removing the resisting force thereby allowing the alloy to transform to its austenitic state and the shape of the article to be restored substantially to the first configuration.
• the article of manufacture is a medical device.
• the method further includes the step of positioning the deformed article within the human body while the deformed article is restrained by the restraining means.
• the step of heating is a step of automatically warming to body temperature when the article is positioned in or near the human body, body temperature being above the alloy's A f temperature.
• the method further includes the step of positioning the deformed article within the human body.
• the restraining means is body tissue.
• the step of heating is a step of automatically warming to body temperature when the article is positioned in or near the human body, body temperature being above the alloy's A f temperature.
• the method further includes the step of cooling prior to the step of deforming, and the step of cooling includes cooling the article to the first temperature such that the shape memory alloy transforms, at least partially, into its stable martensitic state.
• the step of cooling includes cooling the article from the alloy's austenitic state to a state wherein the alloy is at least partially in its stable martensitic state.
• the step of heating includes heating the article until A f , that the shape memory alloy preserves its stable martensitic state.
• the step of heating is a step of automatically warming to body temperature when the article is positioned in or near the human body, body temperature being above the alloy's A f temperature.
• the step of heating includes the step of heating to above the alloy's A f temperature.
• the first temperature is below M s .
• the first temperature is below M 5 and the second temperature is above A f .
• the first temperature is below A f and the second temperature is above A f .
• the step of removing is effected isothermally.
• the restraining means in the step of applying is body tissue
• a deformation is effected in the step of deforming by a means for deforming which is the same means as the restraining means in the step of applying.
• the resisting force in the step of applying is substantially a continuation of the deforming force provided in the step of deforming employed to deform the article.
• the step of deforming includes a deformation effected by a means for deforming which is the same means as the restraining means in the step of applying.
• the restraining means in the step of applying is body tissue.
• a selectably deformable article of manufacture is adapted to have selectable first and second predetermined configurations, the article being formed at least partly of a shape memory alloy.
• the shape memory alloy is at least partially in its stable martensitic state and at a first temperature, thereby facilitating deformation of the article from the first predetermined configuration to the second predetermined configuration.
• the shape memory alloy is further transformable from the stable martensitic state to a metastable stress-retained martensitic state, when heated to at least a second temperature in the presence of a predetermined resisting force.
• the resisting force impedes transformation of the shape memory alloy from the metastable stress-retained martensitic state to an austenitic state and thereby also impedes reversion of the article of manufacture from the second predetermined configuration to the first predetermined configuration.
• the first temperature is below M s . In another embodiment, the first temperature is below A f . In yet another embodiment of the article the second temperature is above A f . In a further embodiment of the article, the second temperature is lower than normal body temperature.
• the stable martensitic state is attained by cooling the alloy to a first temperature below its M s temperature from above its A f temperature. In another embodiment of the article, the metastable stress-related martensite transforms to the austenitic state upon removal of the resisting force and the article reverts to its first configuration from its second configuration.
• the article of manufacture is a medical device. Often when a medial device is used the second temperature is substantially body temperature and A f is below body temperature.
• the medical device may be a surgical clip, an anastomossis ring for crimping adjacent intussuscepted organ wall portions against a generally tubular crimping support element, a staple for bone fixation, an expandable bone fastener, an expandable bone anchor, a coil or mesh stent for disposing in a human vessel so as to provide improved liquid circulation therethrough, an intrauterine device, a heart valve retaining ring, a clamp device for securing tissue, and a blood vessel filter.
• the second temperature is lower than body temperature and A f is below the second temperature. In still other embodiments of the deformable article of manufacture, the second temperature is body temperature, body temperature being above the alloy's A f temperature.
• Fig. 1 illustrates the martensite/austenite phase transformations as a function of temperature for a shape memory alloy (PRIORART);
• Fig. 2 is a schematic representation of the phases (states) in a shape memory alloy subjected to controlled stress and temperature changes;
• Figs. 3A and 3B are schematic representations illustrating the shape memory effect of a device subjected to controlled stress and temperature changes (PRIOR ART);
• Fig. 4 is a schematic representation illustrating the different microstructures possible in shape memory alloys and the macroscopic changes of a device made from such alloys resulting from such changes in microstructure
• Fig. 5 is a schematic representation illustrating the superelasticity effect of a device subjected to controlled stress changes (PRIOR ART);
• Fig. 6 is a schematic representation illustrating the superelastic plasticity (SEP) effect of a device subjected to controlled stress and temperature changes
• Fig. 7 is a schematic representation illustrating the phase transformations between austenite and stress-induced martensite (SIM) subjected to controlled stress and temperature changes (A f > body temperature) (PRIOR ART);
• Fig. 8 is a graphical representation of force versus closing distance in shape memory alloy staples based on SIM (A f > 37°C) and SRM (A f ⁇ 37 0 C);
• Fig. 9 is a graphical representation of comparative loading force versus extension applied to shape memory alloy staples based on SRM (A f ⁇ 37 0 C) and SDVI (A f ⁇ 37 0 C);
• Fig. 10 is a schematic illustration of a surgical clip and cross-sectional views thereof
• Fig. 11 is a schematic illustration of an anastomosis ring and cross-sectional views thereof
• Fig. 12 is a schematic illustration of an anastomosis ring in crimping engagement against a crimping support element
• Fig. 13 is a schematic cross-sectional view taken from Fig. 12 indicating an anastomosis ring in crimping engagement with an intussuscepted hollow organ portion;
• Fig. 14 is a schematic perspective view of a closed bone staple
• Fig. 15 is a schematic perspective view of an open bone staple
• Fig. 16 is a schematic perspective view of an open bone staple applied to a fractured bone
• Figs. 17 A and 17B are schematic views of a bone anchor in its closed and open positions respectively;
• Fig. 18 is a schematic view of an expandable bone fastener;
• Fig. 19 is a schematic perspective view of the bone fastener in Fig. 18;
• Fig. 20 is a schematic perspective view of the bone fastener in Fig. 18 with closed anchoring projections;
• Fig. 21 is a schematic view of a coil stent
• Fig. 22 is a schematic view of a vessel filter prior to final installation
• Fig. 23 is a schematic view of the vessel filter of Fig. 22 after installation
• Fig. 24 is a schematic perspective view of a clamp in an open configuration
• Fig. 25 is a schematic perspective view of the clamp of Fig. 24 in a closed configuration
• Figs. 26A and 26B area schematic views of a dental implant before and after implantation respectively.
• Fig. 27 is a schematic view of a retaining ring for use with an artificial heart valve.
• the present invention inter alia teaches a method for using a device, typically a medical device, formed, at least in part, from a shape memory alloy.
• the method makes use of an effect referred to herein as the superelastic plasticity (SEP) effect.
• SEP superelastic plasticity
• SRM stress-retained martensite
• SEP superelastic plasticity
• the SEP effect used in the method of the present invention represents an SMA's transformation from at least a partially martensitic phase to its austenitic phase via its metastable martensitic phase.
• Fig. 6 schematically illustrates the steps in applying the SEP effect to a device formed from an SMA having SRM properties. The steps illustrated are as follows.
• Cooling 70 a device from the SMA's austenitic state to a temperature where the SMA is at least partially martensitic. During this step the device retains its original shape.
• the starting and ending temperatures for cooling 70 shown in the Figure are typical non- limiting values. However the lower temperature must be below A f .;
• Heating 78 the restrained device to a temperature in excess of A f , thereby causing a transformation from the alloy's deformed martensitic state to a stress-retained martensitic state.
• the stress-retained martensitic state is represented by the region of the graph above diagonal CC line 14. Typically, but without being limiting, this heating may be effected by warming to body temperature (37 0 C);
• a stent is cooled 70, deformed 72, and the deforming load removed 74.
• the stent is then disposed 76 in its deformed shape into a suitable instrument, such as a catheter, where it is restrained 76 and allowed to warm 78.
• a suitable instrument such as a catheter
• the medical device is cooled 70 to a martensitic state, disposed and deformed (opened) 72 by an applicator device.
• the clip As the clip warms 79 directly to ambient temperature, the clip is restrained 76 in its open, deformed configuration by the same applicator device.
• the stent two different devices are used, one for deforming the stent by applying 72 the original load and another, the catheter, for restraining 76 the SMA device during warming.
• a single device may be used, first to apply 72 a load to deform the clip and then to restrain the device when it is heated 79. Accordingly, removing step 74 may or may not be required depending on the device used.
• human tissue may serve as the restraining means.
• fractured bone tissue acts as the restraining device during the warming process.
• a staple is cooled 70, deformed 72, and the deforming load removed 74.
• the staple is then disposed using a cooled pincer into special holes in the bone tissue where it is restrained and allowed to warm 78. No external shape restraining applicator or device is required.
• Bone tissue restrains the staple in its deformed SRM state. Gradually, the staple's legs cut into the bone tissue, and the staple returns to its original shape with the SMA from which the staple is formed transforming 80 from SRM to austenite.
• the step of removing 80 discussed may be done gradually and may not include the removal of the entire resisting force.
• the venous tissue may continue to apply a small resisting force which will prevent the stent from completely recovering its original shape.
• Bone staples gradually return to substantially their initial shape as osteosynthesis proceeds.
• the step of removing 80 is a physiological change resulting in a decrease in the load without its complete removal.
• the step of cooling 70 is optional; there may be instances wherein the SMA of the device is already in a partially martensitic state and the step of cooling 70 is unnecessary.
• FIG. 7 schematically shows a prior art, temperature-manipulated, SIM transition at temperatures below Af but above M 5 .
• Application of a deforming stress 50 to an SMA in a 100% austenitic state produces a deformed macrosopic device (large parallelograms in the upper row) and a stress-induced martensitic microstructure (small parallelograms within the large parallelograms).
• Heating 51 and 52 from within the temperature range M s to Af to a temperature above Af results in the formation of metastable martensite.
• the alloy has an A f > body temperature (BT). It should be remembered that stable austenite is only present in the region below diagonal CC line 14. On cooling 54 to body temperature (37 0 C), the device remains deformed and the alloy exists in a stable deformed martensitic state (middle parallelogram, upper row).
• the device typically a medical device such as a bone staple, does not revert fully to its original shape.
• the device bottom parallelogram also remains somewhat deformed after removal 56 of the deforming stress, and only an incomplete recovery of the applied deforming force is obtained. After removal 56 of the deforming stress, the SMA continues to have a deformed martensitic microstructure.
• Fig. 7 illustrates use of SIM but the Figure indicates that there is little shape restoration. In effect, therefore, if A f > body temperature (BT), the desired work of a SIM- based SMA device can not be attained since substantially complete shape restoration can not be obtained.
• a f > body temperature (BT) body temperature
• Fig. 7 are typical, but non-limiting, working temperatures in prior art medical devices using SMAs.
• the main point in the Figure is that typical prior art uses alloys where BT ⁇ A f .
• Fig. 7 should be viewed in conjunction with Fig. 4 where the macroscopic condition of the device and the microstructure of the alloy are illustrated.
• Figs. 8 and 9 represent an experimental comparison between bone staples using the SEP effect based on SRM and the SME and the SE effect based on SIM. Inter alia they reveal advantages of SRM over SIM.
• the tests described below were performed using a force tester equipped with a monitored temperature cell for cooling and heating.
• Fig. 8 shows a comparison of available force versus closing distance between bone staples made from shape memory alloys having SIM and SRM properties. The results discussed in relation to Fig. 8 are equally applicable to other types of devices made from SMAs using these properties.
• SMA staple 57 using SIM properties underwent stress and temperature changes similar to those shown in Fig. 7.
• the SMA had an A f > body temperature.
• the SMA staple 58 using SRM properties underwent stress and temperature changes similar to those shown and discussed in conjunction with Fig. 6.
• the SMA in staple 58 had an A f ⁇ body temperature.
• Curve associated with staple 57 indicates the recovered force available from a bone staple constructed from an SMA having an A f temperature (42°C) higher than body temperature (37 0 C).
• the staple was stretched to 3.5mm at 20 0 C, heated to 45-5O 0 C and then cooled to about body temperature.
• As the closing distance was reduced that is, as the distance between the test machine's grippers was reduced, recovery of the staple's original shape was incomplete. The recovery was only about 0.5 mm.
• Curve associated with staple 58 indicates the recovered force available from a bone staple constructed from an SMA having an Af temperature (2O 0 C) lower than body temperature (37 0 C).
• the staple was stretched to the same 3.5mm at O 0 C and heated directly to 37 0 C.
• the maximum value of the "recovered" force for the SRM staples was about twice the maximum force "recovered” from the SIM staples.
• One of the staples employed the SEP effect based on SRM while the second staple used the SE effect based on SIM.
• the SE effect is effectively the same as that shown in Fig. 5 while the SEP effect based on SRM is effectively the same as that shown in Fig. 6.
• the staples were mounted on a force tester and gradually opened to a distance of 2.5 mm at different temperatures. Gradually, the grippers of the force tester were brought closer together, allowing the staple to close.
• a load of up to 60 N was needed to open the staple using SEVI properties at a temperature of 24 0 C (curve 60).
• the temperature was increased to body temperature (37°C) (69) and the "recovered” load, the result of the transformation from SIM to austenite, is shown in curve 62. This is the SE effect.
• the required load to deform and open the staple using SRM properties at O 0 C was about 26 N (curve 64).
• the temperature was increased to body temperature (37 0 C)
• Recovery curves 62 and 68 for SIM and SRM devices respectively are very similar. However, the respective applied loads, curves 60 and 64, are different with the load required to deform SIM being about 2.5 times greater than that required to deform SRM.
• This feature represents a substantial advantage for the use of SRM instead of SIM in devices, such as bone staples, clips and stents and other similar devices. It is also clear from the Figure that a much larger part of the applied load is "recovered” with SRM staples. Another advantage, not readily recognizable from the Figure, is that in the case of bone staples and other similar devices, SRM does not require a special shape-retaining instrument when applying the device to the body site. Body tissue can be used as the shape-retaining "instrument".
• the SEP effect must occur with an SMA in at least a partial martensitic state.
• a f is set below the working temperature in SMA-based devices using the SEP effect.
• a f is set below body temperature when an SRM-based medical device is employed.
• SEP shape restoration does not require external heating in SRM-based medical devices since the body typically serves as the heat source. After heating, shape is restored by load removal, typically, but not necessarily, at isothermal conditions.
• the SEP effect enables substantially complete recovery of the device's original shape, thus providing long-term compression on body tissues.
• the SEP effect generally allows for the recovery of more of the applied load than the SE effect while the initial deforming load for the former is significantly less than the latter. Additionally, the SEP effect can often be effected in medical devices without using special restraining devices. Body tissue, such as bone, may be used as the restraining means.
• SRM shape memory alloy
• a surgical clip generally referenced 110, illustrated in an open configuration.
• Clip 110 is typically wire-like, formed at least partly of a shape memory alloy, and is of a coiled configuration so as to include a pair of loops referenced 112 and 114, having respective ends referenced 116 and 118.
• Each of loops 112 and 114 defines a complete circle from its end to a point referenced 120 midway along the coil.
• coil 110 defines two complete circles from end 116 of loop 112 to end 118 of loop 114.
• clip 110 of the present invention are illustrated as defining circular shapes, it will be appreciated by persons skilled in the art that the present invention may, alternatively, define any closed geometric shape, such as for example, an ellipse.
• Surgical clips formed having other configurations are used where surgically appropriate, in accordance with the organ size, position and other factors.
• clip 110 While the entire clip 110 may be formed of a shape memory alloy, it is essential that at least an intermediate portion generally referenced 122 of clip 110 is formed of a shape memory alloy displaying SRM behavior.
• clip 110 When the clip is mounted on an applicator device and cooled to or below a predetermined first temperature, clip 110 transforms to a plastic martensitic state. Loops 112 and 114 may be moved apart by the applicator as seen in Fig. 10. When heated to or above a second temperature, which is typically below body temperature, and while a resistance force is applied by the applicator so as to keep loops 112 and 114 in a spaced-apart configuration, the stressed shape memory alloy transforms to a metastable stress- retained martensitic state.
• FIG. 10 there are seen cross-sectional views of alternative profiles taken along line 1-1 of surgical clip 110.
• a generally circular cross-sectional profile referenced 126 having planar surfaces referenced 128 formed therein according to an alternative embodiment of the present invention, an elliptical profile referenced 130, and an elliptical-type profile referenced 132.
• an anastomosis ring generally referenced 140, which is configured from a length of shape memory alloy wire 142 as a closed generally circular shaped ring, having a central opening referenced 144, a predetermined wire thickness and overlapping end portions referenced 146 and 148.
• FIG. 11 there is also seen a cross-sectional view of overlapping end portions 146 and 148 of anastomosis ring 140 as taken along line 11-11.
• Each of end portions 146 and 148 has a flat contact surface referenced 150 formed thereon so as to provide a similar cross-sectional profile at overlapping portions 146 and 148 as wire 142.
• the cross-section of the wire forming ring 140 may be varied, in accordance with alternative embodiments of the present invention, hi Figure 11 there are further seen cross-sectional views, which are non-limiting examples only, of alternative profiles taken along line 12-12 of surgical clip 140. There is seen a generally circular cross- sectional profile referenced 152. According to an alternative embodiment of the present invention, there is seen an elliptical profile referenced 154.
• the shape memory alloy of anastomosis ring 140 When cooled to or below a first temperature, the shape memory alloy of anastomosis ring 140 assumes a stable plastically malleable martensitic state, and an elastic austenitic state, when warmed to or above a second, higher temperature. This stable martensitic state facilitates that anastomosis ring 140 is expanded and retains an expanded configuration at the first, lower temperature. Once ring 140 is warmed to, or above, the second temperature, without the imposition of a resisting force, ring 140 returns substantially to the original configuration. However, imposing a resisting force thereto by a resistance means, so as to resist clip
• FIGs. 12 and 13 there is seen, respectively, a perspective and a cross- sectional view of anastomosis ring generally referenced 140 in crimping engagement with a crimping support element referenced generally 160, in accordance with an embodiment of the present invention.
• the cross-sectional view seen in Figure 13 is taken along line 15-15 in Fig. 12.
• the Figure also shows intussuscepted adjacent walls 162 of organ portion 163.
• Crimping support element 160 includes a short tubular section referenced 164 with an opening referenced 165 therethrough, proximal and distal end lugs referenced 166 and 168 respectively.
• An anastomosis ring 140 is cooled to a reduced temperature, below body temperature, where the shape memory alloy transforms from its austenitic to its martensitic state. Ring 140 is easily deformed to an insertable size, so as to fit onto a cooled restraining means of an anastomosis apparatus (not shown). By warming to or above a second temperature, anastomosis ring 140 attempts to revert to its original configuration.
• the alloy exhibits SME behavior (Figs. 3A and 3B) and a device may be implanted in a martensitic state. Brief heating will be required to transform the alloy to a metastable martensitic phase, and on re- cooling to body temperature, the metastable martensite returns to a stable martensite state. However, the alloy does not provide complete shape restoration and the compression force is very much reduced. Figure 8, as discussed above, shows the reduced shape recovery.
• the alloy has an A f temperature below body temperature, the alloy exhibits SE (SHVI), and the force needed to deform a bone staple is substantially greater than the force applied by the staple to a bone fracture when the staple's shape is restored. This was discussed in conjunction with Fig. 9 above.
• SRM utilization provides almost full shape restoration in the presence of a permanent compression force referenced 58 in Fig. 8.
• the force necessary for shape deformation of a staple in a stable martensitic phase is much smaller than when the alloy is in an austenitic state, as discussed above in conjunction with Fig. 9.
• Figs. 14, 15 and 16 in accordance with an embodiment of the present invention, there are seen respectively the closed, open and inserted configurations of a bone staple.
• bone staple referenced 200
• the SMA is transformed into a stable martensitic state
• the staple is relatively easily deformed to the open configuration referenced 202 shown in Figure 15.
• staples 206 although naturally warmed to body temperature, remain in a martensitic state.
• the alloy is no longer in a stable martensite state, but has been transformed into a stress-retained martensite state.
• staples 206 attempt to revert to their closed configuration 200, providing a predetermined stressing force to the fracture site 208 as the alloy attempts to revert to its austenitic state.
• the physiological process of fracture consolidation takes at least two weeks.
• a reconstruction of bone cells takes place at fracture site 208.
• end portion legs referenced 210 of staples 206 are transformed to a closed configuration 200 by apparently "cutting" through the bone 204.
• the transformation of SRM to austenite provides an almost constant stress at the fracture site.
• Bone Anchor Referring now to Figs. 17A and 17B, in accordance with an added embodiment of the present invention, the mechanism for utilizing a bone anchor generally referenced 220 is substantially similar to that required for bone staples, as disclosed herein above in conjunction with Figs. 14, 15 and 16.
• a hole (not shown) is drilled into a bone.
• Bone anchor 220 is pre-cooled so that the shape memory alloy of anchor arms referenced 226 is transformed into its stable martensitic state. As indicated in Fig. 17A, arms 226 are deformed against a fastener body referenced 228. Thereafter bone anchor 220 is positioned in the hole in the bone.
• Body heat warms fastener 220 to body temperature, causing arms 226 to deflect outwards as shown in Fig. 17B against the inner surface of the hole, which provides a resisting force thereto.
• the alloy of arms 226 is transformed into its SRM state.
• the stress-retained martensite attempts to transform into austenite, thereby to cause anchor 220 to be anchored into the bone.
• SRM allows ease of deformation without the need for restraining arms 226 in a closed position but using a special restraining placement device in some cases may be useful.
• FIGs. 18-20 there are seen, in accordance with an added embodiment of the present invention, schematic views of a expandable bone fastener generally referenced 250 having a generally cylindrical body referenced 252 and at least one pair of fastening projections referenced 254 formed from a shape memory alloy.
• fastener 250 is shown as having two pairs of projections 254. While in an austenitic state, projections 254 remain in an open configuration as indicated in Figures 18 and 19.
• the mechanism for utilizing a bone fastener 250 is substantially similar to that required for bone staples, as disclosed herein above in conjunction with Figs. 14, 15 and 16.
• a hole with a diameter to facilitate insertion is drilled into the bone (not shown).
• fastener 250 Prior to insertion, fastener 250 is cooled so as to cause a transformation of the shape memory alloy to a fully martensitic state so that projections 254 are plastically deformable.
• projections 254 are drawn together so as to form a substantially cylindrical configuration generally referenced 256 when the alloy is in its martensitic state. Bone fastener 250 is then positioned in the drilled hole in the bone.
• Body heat warms fastener 250 to body temperature, causing projections 254 to deflect outwards against the inner surface of the hole, providing a resisting force thereto.
• the shape memory alloy of projections 254 is thereby transformed into an SRM state, as the stress-retained martensite attempts to transform into austenite. Projections 254 deflect outwards causing fastener 250 to be fastened into the bone.
• SRM allows ease of deformation without the need for fastening projections 254 in a closed position and without the need for a special placement device. This contrasts with the use of an SIM alloy for a bone anchor, where the anchoring projections need to be forced into a closed elastic configuration prior to insertion and have to be inserted using a special placement device.
• Carotid angioplasty and stenting are alternatives to surgery for the treatment of atherosclerotic carotid arteries, and randomized clinical trials.
• the biocompatibility and shape recoverability of shape memory alloys make them useful for this procedure.
• the self-expanding stent (coil or mesh) diameter is preset to be somewhat larger than that of the target vessel.
• the opened stent is crimped or straightened, leading to a phase transformation to stress-induced martensite, restrained in a delivery system such as a catheter and then elastically released into the target vessel.
• the main difficulties arising from using a SDVI alloy stent are restraining the deformed stent in its metastable martensitic phase, and preventing it from regaining a preset shape prior to final insertion into a restraining means such as a catheter. If an SRM element is used, the preparation prior to insertion is easily accomplished. Referring now to Fig.
• a coil stent generally referenced 230 formed from a shape memory alloy wire referenced 232 in the shape of a helical coil.
• Coil stent 230 is cooled to a reduced temperature, below body temperature, when the shape memory alloy is transformed from an austenitic to a martensitic state.
• Stent 230 is easily deformed to an insertable size and shape generally referenced 234, so as to fit into a cooled delivery applicator or catheter referenced 236.
• Coil 230 retains its insertable size and shape 234 without requiring any restraining instruments. It is easily inserted while cool into cooled catheter 236. This aspect is especially important when using long stents.
• the alloy transforms from its stable martensitic state to its metastable stress-retained martensitic state, when heated to an ambient temperature and in the presence of a restraining catheter. Subsequent insertion into a vessel is accomplished by pushing coil stent from catheter 236. Expansion occurs immediately to a preset size referenced 238 as stent 230 is released from catheter 236 and the alloy reverts to its austenitic state.
• FIGs. 22 and 23 there are seen, in accordance with an additional embodiment of the present invention, schematic views of a vessel filter generally referenced 260 prior to and after final installation respectively.
• filter 260 After being cooled to an at least partially martensitic state, generally about O 0 C, filter 260 is deformed so as to be insertable into a catheter referenced 262 equipped with a pusher device referenced 264. While in catheter 262, filter 260 is warmed. The restrictive force of catheter 262 prevents filter 260 from reverting to an austenitic state, and correspondingly to its original shape.
• the stable martensite of the alloy undergoes transformation to a stressed retained martensitic (SRM) state.
• SRM stressed retained martensitic
• Catheter 262 is introduced into a pre-selected blood-vessel referenced 266.
• filter 260 is ejected from catheter 262 into blood vessel 266.
• the SRM state of the alloy of filter 260 transforms to its austenitic state.
• Primary 263 and secondary 265 elements expand to their original shape and lodge in blood vessel 266.
• Primary 263 and secondary 265 elements form primary and secondary supporting webs referenced 267 and 268 respectively. Any blood clots borne in the blood stream impinge against supporting webs 267 and 268 and are fragmented thereby.
• Intrauterine Devices IUD
• Figs. 24 and 25 show schematic perspective views of a clamp generally referenced 270 in an open and in a closed configuration, respectively.
• connecting portion referenced 274 Prior to use, connecting portion referenced 274 is cooled so as to cause the shape memory alloy from which clamp 270 is constructed to transform to a plastic martensitic state.
• Clamp jaws referenced 272 are moved apart and retain this deformed shape as indicated in Fig. 24.
• connecting portion 274 is warmed by body heat causing the alloy to begin to revert to an austenitic state. As the shape begins to revert to the closed configuration shown in Fig.
• jaws 272 engage the selected tissue therebetween.
• the presence of the interposed tissue exerts a resisting force on clamp 270, specifically on connecting portion 274, preventing complete restoration of the original fully closed shape.
• This allows the martensite of the alloy to be transformed into stress retained martensitic (SRM), and, while the SRM transforms to an austenitic state, clamp 270 exerts a continuing clamping force on the engaged tissue.
• SRM stress retained martensitic
• clamp 270 is restrained in a suitable applicator prior to use, and the resultant warming results in SRM formation.
• FIG. 26A shows the implant prior to implantation while Fig. 26B shows the implant after implantation into jawbone 285.
• Implant 280 includes a body portion referenced 282 and a plurality of projections referenced 286 formed of a shape memory alloy. When at body temperature, that is when dental implant 280 is implanted into jawbone 285, projections 286 are in an austenitic state and are configured to project radially outwards from body 282 as in Fig. 26.
• dental implant 280 Prior to implantation (Fig 26A), dental implant 280 is cooled so as to transform the alloy of projections 286 to a plastic martensitic state. As shown in Fig. 26A, projections 286 are folded circumferentially. Prior to implantation, projections 286 are inserted into a cooled holding tool referenced 288 so as to retain the projections in a martensitic state and in their folded configuration. Dental implant 280 is inserted into a selected jaw-bone 285 cavity in Fig. 26B and allowed to warm to body temperature. The alloy begins to revert to an austenitic state and folded projections 286 of Fig 26A begin to revert to the extended projection 286 configuration of Fig. 26B.
• Projections 286 open outwards and come into engagement with the jawbone 285 cavity which applies a resisting force.
• the alloy transforms into stress retained martensitic (SRM) state and applies a continuing force to the bone 285 cavity so as to remain permanently engaged therein
• SRM stress retained martensitic
• Jervis in US 6,306,141, describes the use of a SIM ring to hold a sewing cuff to a body of an artificial heart valve. It is claimed that SIM alloys will provide the best alternative for this purpose.
• the ring is expanded from its initial austenitic state with the transformation to SIM.
• the stress required to strain an object in an austenitic state is several times higher than when the object is in a martensitic state.
• the ring is positioned about the valve body, heated above A f and then cooled to its original temperature. This procedure causes the ring to engage the valve body to the heart.
• FIG. 27 in accordance with another embodiment of the present invention, there is seen a schematic view of a shape memory alloy sewing ring 290 having spines (hooks) 294. Ring 290 is covered by a fabric seal (cuff) referenced 292, to prevent an infiltration between an artificial heart valve and a heart (not shown), utilizing a retaining ring (means) 293. Ring 290 is cooled to transform the alloy from which it is constructed from its austenitic to its malleable martensitic state so that hooks referenced 294 of sewing ring 290 are distortable to an open configuration.
• retaining ring 293 is placed in position over sewing ring 290 and allowed or caused to warm to or above the original temperature.
• the heart valve provides a restraining means and exerts a resisting force against closure of ring 290, resulting in the formation of stress retained martensite (SRM) in the alloy of ring 290.
• SRM stress retained martensite

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